Sprinkle tenderloins lightly with salt and pepper.
Place pork in a slow cooker sprayed with non-stick cooking spray.
Combine syrup, garlic, mustard, honey, brown sugar, vinegar, and thyme. Pour over the pork.
Turn pork to coat thoroughly.
Cover and cook on LOW for 7 to 8 hours, or on HIGH for 3 to 4 hours.
Remove pork to a plate and cover with foil to keep warm.
Pour the juices into a saucepan and bring to a boil over medium heat.
Simmer for 5 minutes.
Combine the cornstarch and cold water; whisk into the reduced juices and cook for 1 minute longer.
Slice the pork and serve with the thickened juices.